Journal of Intellectual Disability Research 372 pp – Blackwell Science, LtdOxford, UKJIRJournal of Intellectual Disability Research-Blackwell Publishing Ltd, 5372378Original ArticleTheory of mind deficits in children with FXSK. Cornish et al. Theory of mind deficits in children with fragile X syndrome K. Cornish1,2,3, J. A. Burack1,3, A. Rahman1,3, F. Munir4, N. Russo1,3 & C. Grant5 1 Department of Educational Psychology, McGill University, Montreal, Canada 2 Department of Neurology and Neurosurgery, McGill University, Montreal, Canada 3 Canadian Centre for Cognitive Research in Neurodevelopmental Disorders, Montreal, Canada 4 Institute of Work, Health and Organizations, University of Nottingham, Nottingham, UK 5 School of Psychology, University of Birmingham, Birmingham, UK Abstract revealed qualitative differences in error types (realist vs. phenomenist), suggestive of atypical development Background Given the consistent findings of theory that goes beyond general cognitive delay. of mind deficits in children with autism, it would be Conclusion The findings are discussed in terms of extremely beneficial to examine the profile of theory the teasing apart of different components of social of mind abilities in other clinical groups such as frag- cognition in order to identify syndrome-specific defi- ile X syndrome (FXS) and Down syndrome (DS). ciencies and proficiencies. Aim The aim of the present study was to assess whether boys with FXS are impaired in simple social Keywords autism, developmental psychopathology, situations that require them to understand their own Down syndrome, fragile X syndrome, social and others’ mental states – in essence: do they have cognition, theory of mind a ‘theory of mind’? Method Well-standardized tasks of theory of mind, the location change false belief task and the Introduction appearance–reality tasks were employed to examine Fragile X syndrome (FXS) is the world’s most com- whether any impairment might be specific to the mon form of hereditary intellectual disability (ID), FXS or part of a more generalized developmental with a prevalence of in male births and in deficit. female births and it is a result of silencing of a Results The results suggest that children with FXS single gene, the fragile X mental retardation- do have impairment in theory of mind that is com- (FMR) gene (de Vries et al. ; Turner et al. parable to the deficit reported in other groups with ). In recent years, it has become one of the learning disabilities such as DS. However, closer most widely researched and well-documented of inspection of the impairment between these groups genetic conditions. At a genetic level, it is now established that the FMR gene is the major con- tributor to the pathogenesis of FXS and that the key Correspondence: Kim Cornish, Canada Research Chair in Neuropsychology and Education, McGill University, McTavish issues relate to a lack of messenger RNA (mRNA) Street, Montreal, Canada (e-mail: [email protected]). and a lack or absence of the protein product of the © Blackwell Publishing Ltd Journal of Intellectual Disability Research 373 K. Cornish et al.•Theory of mind deficits in children with FXS FMR gene – FMRP. The extent to which these (Fisch ; Bailey et al. ; Dykens & Volkmar discoveries explain some of the phenotypic out- ) and around –% of children with FXS meet comes in FXS are beginning to be unravelled with the diagnostic criteria for autism (Reiss & Freund the application of more finely tuned neuropsycho- ; Turk & Graham ; Dykens & Volkmar ; logical and neuropsychiatric approaches to under- Bailey et al. ). Yet, despite these commonalities, standing atypical development. In normal certain social abilities that are particularly deficient individuals there are – repeats with repeats among children with autism remain relatively intact found on the most common allele (DNA sequence in children with FXS, including recognition of emo- at FMR- gene site). Alleles with between – tion and face perception (Simon & Finucane ; repeats are called premutations and generate some Turk & Cornish ) and conversational abilities protein. When or more CGG repeats are (Sudhalter ). So while similarities between syn- present, there is hypermethylation and a subsequent dromes are present, the differences in behavioural silencing of the FMR gene. This is commonly characteristics necessitate the development of cogni- referred to as the FMR full mutation. tive and behavioural profiles of intact and impaired At a cognitive level, the syndrome presents with abilities in FXS that will facilitate comparisons mild to severe ID, severe problems of inattention and between related disorders. hyperactivity (Turk ) and uneven abilities across One way to test the association between FXS and and within cognitive domains. Relative strengths in autism would be to assess ‘theory of mind’ among language accompany relative weaknesses in visuospa- children with FXS because the deficit in ‘theory of tial cognition (Freund & Reiss ; Cornish et al. mind’ appears to underlie many of the social and ) and executive functioning, most notably for communicative impairments that are characteristic of skills that require sequential processing, short-term autism (for a review see Yirmiya et al. ). Much memory recall, or reproduction of items in a serial or of the research about ‘theory of mind’ ability relies temporal order (Jakala et al. ; Wilding et al. on false belief (FB) tasks as indicators of whether or ; Cornish et al. a). In contrast, performance not a child has mental state understanding. Children is relatively good on skills requiring simultaneous with autism show pronounced deficits in mental state rather than sequential information processing, or on understanding or the commonly used FB tasks, in face and emotion recognition (Hodapp et al. ; which one’s understanding of the event or situation Turk & Cornish ). must be differentiated from others, or appearance– At the behavioural level, certain problems associ- reality (AR) tasks, in which one must distinguish ated with FXS appear to reflect a link with autism. between the perception of an object (its appearance) For example, children with FXS show some impair- and their knowledge of it (its real identity) (Baron- ments in social and communicative functioning Cohen ). On the AR tasks, children with autism (Reiss & Freund ; Lachiewicz ; Turk & Cor- make significantly more overall errors than children nish ), two of the three domains that comprise with Down syndrome (DS). More specifically, chil- the triad of impairments that are central to the cur- dren with autism make qualitatively different types of rent diagnostic systems of autism (APA ). Within errors (phenomenist) compared with children with these domains, both groups display language delay, DS who make an equal number of phenomenist and echolalia, and perseverative speech (Hagerman et al. realist errors (see Method section for examples of ; Cohen et al. ; Hagerman et al. ), but these error types). commonalities between the groups also extend to Given the consistent findings of theory of mind attentional difficulties (Baumgardner et al. ; deficits in children with autism, it would be extremely Turk ; Munir et al. a), poor eye contact, and beneficial to examine the profile of theory of mind stereotypic movements (Cohen et al. ; Hager- abilities in other clinical groups such as FXS. Of the man et al. ). The similarities between autism few published studies on theory of mind abilities in and FXS are consistent with evidence of the co- other syndromes, an initial study by Garner et al. occurrence of the two disorders (Cohen et al. ; () reported that more children with FXS failed Feinstein & Reiss ; Bailey et al. ), because standard FB tasks than a comparison group of chil- –% of cases of autism appear to be caused by FXS dren with ID of unknown aetiology. In the present © Blackwell Publishing Ltd, Journal of Intellectual Disability Research , – Journal of Intellectual Disability Research 374 K. Cornish et al.•Theory of mind deficits in children with FXS study, we extend these findings in two main ways. tings. None of the children met the ICD- criteria Firstly, we incorporate a relatively large sample size for autism. Furthermore, none of the children in any of children with FXS. Secondly, by comparing per- of the groups had sensory impairments including formance across two distinct syndromes of known hearing deficits and decreased visual acuity. Finally, aetiology we begin to delineate the specificity of none of the children were on stimulant drugs such as theory of mind deficits across neurodevelopment methylphenidate (Ritalin) for hyperactivity which disorders. might influence cognitive performance. Our objectives were to determine whether young Verbal mental age (VMA) was assessed using the males with FXS, who were screened for autism and British picture vocabulary scale (BPVS) (Dunn et al. did not receive a diagnosis, would display a specific ). The VMA for the FXS group was years and deficit in theory of mind as measured by both FB (i.e. months (range = .–., SD = months). For Sally Anne) and AR tasks, on which the typically the DS group, the VMA was years and months developing trajectory is well-documented (Frith & (range = .–., SD = months). Frith ). Male children with DS (Trisomy ) matched for chronological and verbal mental age Data collection and measures were included as the comparison group because FXS and DS represent the two most common causes of The location change false belief task ID for which aetiology